In recent years, with progresses of digital technologies, electronic devices such as portable information devices and information home appliances have been developed to achieve higher functionalities. With achievement of the higher functionalities of the electronic devices, semiconductor elements incorporated into the electronic devices have been developed at a high pace to attain further miniaturization and a higher speed. Among them, the uses of a non-volatile memory with a high capacity which is represented by a flash memory have been expanding at a high space. Moreover, as a new non-volatile memory in a next generation which has a potential of replacing this flash memory, development of a variable resistance non-volatile memory element including a variable resistance element has been progressing. The variable resistance element refers to an element which has a characteristic in which its resistance value changes reversibly in response to an electric signal applied thereto, and is able to store information corresponding to the resistance value in a non-volatile manner.
As an exemplary variable resistance element, there has been proposed a semiconductor memory device incorporating a variable resistance layer including transition metal oxides which are different from each other in oxygen content atomic percentage and are stacked together. For example, Patent Literature 1 discloses that a redox reaction is caused to take place selectively in a region of an interface between an electrode and a variable resistance layer with a higher oxygen content atomic percentage, contacting the electrode, and resistance change is stabilized.
A variable resistance layer of a non-volatile memory element disclosed in Patent Literature 2 includes a first variable resistance layer and a second variable resistance layer, the first variable resistance layer comprises a first transition metal oxide, the second variable resistance layer comprises a second transition metal oxide and a third transition metal oxide, the second transition metal oxide has a lower oxygen content atomic percentage than the first transition metal oxide and the third transition metal oxide, and the second transition metal oxide and the third transition metal oxide are in contact with the first variable resistance layer.